THE 3IISSING FACTOR IJST CURRENT THEORIES. 15 



Now the rationale of living is revealed for us in proto- 

 plasm. Protoplasm sets life its task. Living can only 

 be done along its lines. There start the channels in 

 which all life must run, and though the channels bi- 

 furcate endlessly as time goes on, and though more life 

 and fuller is ever coursing through them, it can never 

 overflow the banks appointed from the beginning. 



But this is not all. The activities even of the 

 higher life, though not qualitatively limited by the 

 lower, are determined by these same lines. Were 

 these facts only relevant in the domain of physiology, 

 they would be of small account in a study of the 

 Ascent of Man. But the more profoundly the Evo- 

 lution of Man is investigated the more clearly is it 

 seen that the whole course of his development has 

 been conducted on this fundamental basis. Life, all 

 life, higher or lower, is an organic unity. Nature may 

 vary her effects, may introduce qualitative changes so 

 stupendous as to make their affinities with lower 

 things unthinkable, but she has never re-laid the 

 foundations of the world. Evolution began with 

 protoplasm and ended with Man, and all the way be- 

 tween, the development has been a symmetry whose 

 secret lies in the two or three great crystallizing 

 forces revealed to us through this first basis. 



Having realized the significance of the physiological 

 functions, let us now address ourselves to their mean- 

 ing and connotations. The first, the function of 

 Nutrition, on which the Struggle for Life depends, 

 requires no explanation. Mr. Darwin was careful to 

 give to his favorite phrase, the Struggle for Life, a 

 wider meaning than that which associates it merely 

 with Nutrition j but this qualification seems largely to 



